News

Comparison of the angular distribution of satellites galaxies around paired host galaxies between systems observed in SDSS (black) and two cosmological simulations based on the Lambda Cold Dark Matter Model (red and blue).

My newest article (with Rodrigo Ibata and James Bullock), titled “The Lopsidedness of Satellite Galaxy Systems in ΛCDM Simulations“, has now been published by the Astrophysical Journal. It was motivated by a study by Libeskind et al. (2016) in which they discovered a significant preference of satellite galaxies to lie on the side towards a nearby partner galaxy of their host. For this, Libeskind et al. identified nearby pairs of Milky-Way-like galaxies in the SDSS survey, and then measured the angular distribution of their satellite galaxies relative to the line connecting each pair. After stacking the data of thousands of such pairs, they found that there is up to an 8% excess of satellites in the region pointing to the partner galaxy (black line in the figure). This can be considered a lower limit of the true “lopsidedness” because the satellite galaxy sample is most likely contaminated by more randomly distributed fore- and background galaxies. In my new paper, I performed the first-ever comparison of this observed effect with expectations from cosmological simulations.

The Institute of Art and Ideas (IAI) had recently invited me, on rather short notice, to contribute an article to their October issue on the topic Gravity. IAI is the organizer of a big philosophy and music festival (called “HowTheLightGetsIn”), and has a website dedicated to articles, videos, and debates on various topics, all centered around the theme “Philosophy of our times”. They asked me to write about the idea of modified gravity as an alternative to dark matter, and I happily obliged. The article is online now, so check it out here: “Beyond Dark Matter” (side note: I have no clue why they chose the illustration that goes with the article).

You can also enjoy the other articles in this issue, written by a list of distinguished authors: George Ellis writes about what we know about gravity, Sabine Hossenfelder asks whether space-time might be a fluid, David Merritt investigates gravity through the eyes of Karl Popper’s philosophy of science. Andrew Janiak tells the story of how Newton developed his law of gravity, Don Howard looks at how our understanding of gravity has evolved over time, and Valia Allori discusses mismatches between theory and evidence.

My most recent article just got published in Astronomical Notes / Astronomische Nachrichten. It is titled “Considerations on how to investigate planes of satellite galaxies” and discusses a number of essential aspects one should keep in mind when studying planes of satellite galaxies such as the Vast Polar Structure (VPOS) around the Milky Way, and when comparing them to cosmological simulations. It was in part inspired by some recent publications that allege that these satellite structures are not a problem for LCDM cosmology. In the paper, we show that these studies are seriously flawed, since they do not consider observational biases, neglect to make any statistical tests or determine significances of their statements, and ignore observational uncertainties.

It is pretty nice to see a paper of mine published in the world’s longest-running astronomy journal, founded on 1821. Even better, the paper was labelled an “Editor’s Choice”, and they even used one of my plots as the cover image of the issue (see left)!

Earlier this year, a crew working for the Japanese public broadcasting organization NHK visited me at Case Western Reserve University. They interviewed me for their TV show Cosmic Front Next, for an one-hour episode about Globular Clusters featuring a variety of astronomers. I spoke about how the Milky Way might have acquired its system of globular clusters and their connection to the Vast Polar Structure. It was particularly interesting to see how efficiently and thoroughly they re-decorated my office to give it a moody dark-blue light and astronomy-inspired background.

The episode on Globular Clusters has now been broadcasted during their season 5, and NHK kindly send me a DVD. They even produced nice animations illustrating some of the concepts I talked about. What’s particularly funny: they also interviewed my old grad school friend Andreas at Columbia University, and the two of us were featured right after another.

Explaining the concept of dynamical friction acting onto a satellite galaxy as it orbits the Milky Way.

They asked me to pose for some establishing shots, in particular they wanted me to read something in our department’s library. So I picked every dynamicist’s bible.

New Scientist recently ran a cover story on the possibility of a past encounter between the Milky Way and Andromeda galaxies, satellite galaxy planes, and superfluid dark matter as a possible explanation of the MOND phenomenon. I was interviewed for the article a while ago and am quoted quite prominently in it, which is pretty cool.

When the article first appeared I was at a conference in a remote town in Austria, but luckily I could finally grab a copy to satisfy my curiosity when connecting in Heathrow on the way back. For you, that’s much simpler right now: until April 13, you can read this and all other New Scientist articles for free online if you register on their website. So go check it out: “Our Impossible Galaxy“.

Since this is basically common knowledge by now, it probably should be mentioned on my website somewhere. So here we go: I was offered, and have happily accepted, a Hubble Fellowship. This is possibly the best thing that could have happened to me this job season, since it is one of the most prestigious fellowships in astronomy, gives me a great deal of independence, and a very decent research and travel budget, too. And I have to admit, it is pretty cool to see my name in a NASA/Space Telescope Science Institute (STScI) press release announcing the 2016 Hubble Fellows. So, this fall I’ll be moving to the University of California, Irvine. More information on that once I myself have figured out the details.